Conventional pneumatically-operated valves have been available in two types: a normally-open pneumatically-operated valve wherein a fluid passage is constantly kept open by means of a valve section provided upon a piston rod by means of a spring force being applied in one fixed direction, and is closed from the normally open state by applying the pneumatic pressure to the piston against the spring force when a valve closing signal is sensed; and a normally-closed pneumatically-operated valve wherein, normally, a fluid passage is constantly closed by means of a valve section provided upon a piston rod by means of a spring force; and is opened from the normally-closed state by applying the pneumatic pressure to the piston against the spring force when a valve opening signal is sensed.
In connection with the conventional valves, the only methods to obtain a large output in order to open or close the valve section were to increase the pneumatic pressure to be applied to the piston and to increase the piston diameter in order to provide a larger active pressure area. In the former method, however, the strength of the equipment which is subjected to the pneumatic pressure is limited; in small-sized equipment, for example high-pressure air is unusable. On the other hand, in the latter method increasing the piston diameter in order to provide a larger active pressure area is also not suitable for use for small-sized equipment because then the equipment no longer remains small in size.
When pure water as is used in cleaning IC substrates is adopted as the fluid the flow of which is controlled by means of the pneumatically-operated valve, it is essential to properly clean members before assembly in order to prevent the entrance of dust. However, since the valve uses a number of soft elastic members such as O-rings, powerfully cleaning them with ultrasonic waves will produce an undesirable result, such as, for example impairment of these soft elastic members. Furthermore, separately cleaning the soft elastic members such as the O-rings has the drawback that, because of the necessity of installation of the O-rings, the members will frequently come into contact with the O-rings during the assembling operation, resulting in the attachment of dust thereto.
To eliminate these drawbacks, there have been adopted such methods known in the prior art, as disclosed in Laid-Open Japanese Patents No. Sho 61-109973 and No. Sho 61-130682, wherein a valve actuator is formed of two separated parts: a driving member and a valve operating member, and soft substances such as O-rings, which are likely to be impaired by means of ultrasonic cleaning are attached only within the former, and are not used within the latter so as not to be in contact with the clean fluid, so that the valve operating member which comes into contact with a clean solution contained within the fluid passage will be thoroughly cleaned by cleaning the driving member and the valve operating member separately at the time of manufacture and thereafter the driving member and the valve operating member are assembled and connected together. However, where there is the necessity of decreasing the opening-closing stroke of the valve section, for example where there is available the opening-closing stroke of only about 0.6 mm, if the driving member and the valve operating member are assembled into one piston rod, thereby connecting the piston, lock ring, each connecting member, and many members at butting positions between the members, the manufacturing dimensional errors of these members, if slight within each member, will become great when totaled, and moreover when error and play that might occur in assembling the members are added, it will be likely that the opening-closing stroke of approximately 0.6 mm will be absorbed, resulting in a failure in the successful valving action.